1. Field of the Invention
The present invention relates to a welding method and a welding apparatus.
2. Description of the Related Art
Traditionally, arc welding has been used for welding work.
In one type of arc welding, welding current is supplied to an electrode and the second electrode may be connected to ground, and a shielding gas is introduced into the space between electrode and base material, the shielding gas thus ionized generates electrons having kinetic energy. The generated electrons form an arc region between an electrode and the base material. The electrons within the arc region impinge on the base material and impart kinetic energy to the base material which is thus melted.
FIG. 1 is a diagram showing an arc welding apparatus.
The arc welding apparatus comprises: a welding power supply not shown; first electrode 101 to which welding current is supplied from the power supply; the second electrode is not shown; and a cylindrically shaped gas nozzle 102 for supplying a shielding gas along the electrode toward a base material.
To weld the base material, welding current is supplied from the welding power supply to electrode 101 and the second electrode, while supplying the shielding gas through the gas nozzle 102, and an arc region 103 is thus formed between the first electrode and the base material. Since the arc region 103 is held down against the base material by the pressure of the shielding gas being supplied from above, the portion thereof contacting the base material spreads out, increasing the welding width W. That is, the arc area 103 has a shape spreading downward.
In arc welding, therefore, the energy density of the portion of the arc region contacting the base material is low, and as a result, the ratio of the melt depth to the welding width W of the weld zone is small, i.e., in the case of arc welding, the aspect ratio which is the ratio of the melt depth to the welding width W of the weld zone is low. Accordingly, arc welding is neither suitable for welding that requires low distortion nor for high-speed welding, and is mainly used for coarse-precision welding work.
On the other hand, for welding that requires low distortion or for high-speed welding, laser welding is common. With laser welding, a weld zone having a high aspect ratio can be formed because the energy density of the melt zone is high.
Patent documents relating to arc welding include, for example, Japanese Unexamined Patent Publication Nos. H08-267250 and 2003-53543, Japanese Patent No. 2670076, and Japanese Unexamined Patent Publication H11-241168.